Hook inside the body tag or #wrap div for CSS Style

[BadJesus]

I want to use custom fields for an UBER simple to use backend.
I can't seem to figure out how to change the style property for either the body tag or the #wrap div.

The only thing I can think of is adding a custom style class embedded into the header & calling my custom post type inside of a class.

So it would be

<style type="text/css" media=screen>
body.custom_body1 {background:url("<?php my_custom_field(); ?>") no-repeat top center transparent;}
</style>

Then using Wordpress' built in custom body class filter...

// Add specific CSS class by filter
add_filter('body_class','my_class_names');
function my_class_names($classes) {
	// add 'class-name' to the $classes array
	$classes[] = 'custom_body1';
	// return the $classes array
	return $classes;
}

this just seems a bit sloppy though. Is this actually the best way to accomplish this?

Sorry if this doesn't make any sense, it does in my head. :)

Thanks!